Hard freezes with Sierra

I'm experiencing a really annoying freezes/hangs I've never seen before in OSX. Audio continues to play, but everything else freezes and never unfreezes. I can't even open the Force quit dialogue. Only way out is to hold the power button and then restart. Went back to El Capitan, all is fine.

I tried again with 10.12.1, and it's doing it again. Like three times within 6 hours. Rolled back again.

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